I found that reaching the end of the pigtail that connects the passenger side sensor 1 to the pigtail connection on the car IMPOSSIBLE to reach as described in other comments. What I did was to use a long screwdriver and small hammer to knock the pigtail on the car end of the pigtail off its spade clip thus allowing the pigtail to drop down to easy reach. Worked great of me!

I'm 8 hours into passenger side forward sensor. I'm stuck with only being able to remove the sensor about 1/4 revolution. I've sprayed PB blaster on it all day long, but it's a horrible angle to work. (I have a separate thread on my removal process here https://www.clublexus.com/forums/ls-...-pissed-4.html )

For the connector, I removed the 10mm bolt that held the connector's MOUNTING BRACKET to the car. Once that bolt is removed, you can rotate the connector assembly (while it's still on the mounting bracket) and finally realize there's 1 side of the connector, that you push hard with your index finger and you'll hear a magical CLICK. Once you hear that, you'll be able to pull and wiggle and pull and wiggle apart the connector.

I don't know how to remove the sensor from the exhaust pipe. I'm not going to put a torch on it. The only torch in my toolbox is a Tiki torch, not to mention the PB Blaster is flammable.

I'm thinking maybe I should ensure I wiped off all the excess PB Blaster, and maybe START THE CAR and let her heatup for a minute or 2? Has anyone ever started the car with this sensor TOTALLY removed or even loose? What would happen? What would it sound like? I'm getting a sick stomach...

Glad you were able to finally get that sensor unthreaded from the exh manifold. Your situation sounds EXACTLY like what I encountered when I replaced that sensor about 3 yrs ago.

When I finally got the old sensor out, I saw that the threads on the sensor were badly stripped, and I couldn't get the new sensor to thread into the exh manifold for the life of me. I ended up having to buy an O2 sensor tap (should be able to find at most auto parts stores), run the tap into the exh manifold a few times to "reset" the threads, then I was finally/barely able to thread my new sensor in. The whole process was a complete PITA, and I'm certain that if that sensor goes out again, I'm going to have to replace the entire exh manifold as I don't think there's a chance that I will get another sensor to thread into it.

I hope your sensor installation goes smoothly and doesn't turn into what I had to go thru.

Glad you were able to finally get that sensor unthreaded from the exh manifold. Your situation sounds EXACTLY like what I encountered when I replaced that sensor about 3 yrs ago.

When I finally got the old sensor out, I saw that the threads on the sensor were badly stripped, and I couldn't get the new sensor to thread into the exh manifold for the life of me. I ended up having to buy an O2 sensor tap (should be able to find at most auto parts stores), run the tap into the exh manifold a few times to "reset" the threads, then I was finally/barely able to thread my new sensor in. The whole process was a complete PITA, and I'm certain that if that sensor goes out again, I'm going to have to replace the entire exh manifold as I don't think there's a chance that I will get another sensor to thread into it.

I hope your sensor installation goes smoothly and doesn't turn into what I had to go thru.

Regards,
Randy G.

Hey Randy! Don't congratulate me. While I was able to get the old sensor out, I had same situation as you...and UNABLE to thread the new sensor in because the threads were trashed! I have another thread (with pics) going here https://www.clublexus.com/forums/ls-...-pissed-4.html which chronicles my pain, and I do mean pain!!

Hopefully I will have sold my LS before I attempt to do THIS DIY again!

I completed bank 2 sensor 1 on my 2001 LS430 this weekend, it went well. I could not have done it without this forum, thank you all.

My notes:

Buying a sensor removal socket is a must. I tried it without one and utterly failed. The one that worked for me was this.

My sensor came out easily. There was no rust and the threads were perfect. I sprayed PB Blaster a week prior and a few hours prior. Then again, my car has only 36K miles.

The electrical connector was the hardest part by far. I couldn't get my hands close enough to work with it, and the various tools I tried to fashion didn't work. I had to ask my daughter to use her tiny lady hands to do it. She found success by sliding the whole connector off the metal tab. Then I cut the wires near the sensor so I could pull them out and get my hands on the connector. From there it was easy.

Thanks for this write up. It is invaluable along with the vast wealth of other empowering do-it-yourself write ups I've found on these forums. Avoiding the Lexus dealer for service makes me love my car so much more.

I just wanted to post here to thank the creators/curators of this thread. It was extremely helpful for me during my O2 Sensors replacement (did both banks together this past friday).

In my case, my 04 LS430 didn't reset using the Jumper cable on the OBDII connector (the 3rd pin on the "bottom" side of the connector is empty - has no cable going to it), but by jumping the 4th pin with the CG I was able to get access to full code information. While this did not clear the Check Engine code or the VSC codes, it did let me understand there was no issue whatsoever with the VSC itself. I drove my car for few miles on Saturday morning, and after the fourth or fifth stop in my errand run, the codes cleared themselves as the computer cycled thru - Voila! No more alerts on the dashboard.

Thanks again to all that posted and collaborated in this thread throughout the years.

Looks like I'll be able to keep this thread alive for a little while longer. After 3 years (and 64,000 miles) of trouble free driving, I'm getting the CEL with a P0430 code. I made the mistake of unplugging my scanner with the key on, and immediately got the dreaded "Check VSC VSC Off" warning.. So, thanks to my carelessness, I get to reset the VSC as well as swap out the B2S2 O2 sensor.

Hi all, Special thanks to the OP and other contributors to this thread for this very helpful and detailed description; from part numbers, to tools, and how-to's. I was able to change the Bank 1 and 2, Sensor 1 when my CEL went on (code P0135). Even thought he code was for Bank 1 Sensor 1 only, I figured I'd change both just for peace of mind, and went with the Densos. It was a challenge to unplug the wires as everybody mentioned but persistence and patience prevailed. It wasn't exaggeration with regard to the limited space to maneuver my fingers around the plug. What I ended up doing was removing the fastener piece that mounts the entire plug assembly to the car using a couple of long screwdrivers. After they were off, I used the long screw driver to press against the tab while my other hand removed the wire/plug. I then re-fastened the plug housing back to the car. The WD-40 on the threads are a great help.

As everyone had suggested, BE VERY CAREFUL unscrewing the sensor as cross-threading can easily happen. This happened to me on the passenger side: I had the sensor loose already, and while unscrewing, it started feeling tight again. I didn't force it, and just backed it up and tried unscrewing again until it naturally came off. In examining the hole of the opening, I did see a gap on the threads, though I was able to re-screw the new sensor (again carefully because there was a slight gap already). The driver side sensor came off smoothly.

My hands and fingers are sore from the limited space to maneuver and playing around with different ways to unplug the wires, but I'm very happy to have accomplished this task, specially the money savings.

Thanks again to the contributors of this thread. It was a very productive President's day for me.

Thanks @PilotSmith for the original post, and to those who piled on with tips along the way. It empowered to go out and save a big chunk money in the course of doing something manly and satisfying. Everything was really good; the tips on the electrical connectors were key. I might still be under there without them.

Here's my experience, in case it helps others.

I tried this on wheel ramps but no. I went to the auto hobby shop at a not-too-far-away military base to use the lift. I'm glad I did. Doing passenger side first was a good tip, and that one went smooth. The driver side wasn't coming out. When I finally got it to budge, it went around about a turn and then got impossible to move. I figured even if I managed to force it out, I'd mangle the threads and have a tough time getting the new one in. The tool room didn't have the right tools if I needed them, so I stopped and drove home, ordered a thread chaser ($6) and a tap ($15) from Amazon. Reattacked the problem in my driveway.

What worked for me the second time around was:
- tightening the sensor all the way back in before I loosened it (as several suggested if the threads get ****-eyed)
- using a breaker bar and coming in from the side / behind the wheel / above the frame members, rather than from the bottom through the small gaps between the underbody and sump having to use some u joints with extensions **
- I used and think I needed the thread chaser. I did not need the tap, though some Amazon commenters said they did. There were cheaper ones of both but when I've skimped with cutting things in the past, I usually wind up cutting myself so I didnt economize too much

** getting the right work angle on this was, I think, my key problem. I mangled one 3/8 dr u joint at the shop trying to force it from below. I tried giving the o2 sensor tool a whack with a hammer and punch, that got things moving, but is probably what locked the threads up. I think if I had come at it with a breaker bar the first time, I might have finished the job at the shop. However, I didn't think it was possible to come in from that side at that point, i only realized that later after I had been fussing around with the electrical connection.

Other fails:
1) on the re-attack at home, I cut the wires and tried a deep socket, but it wasn't deep enough. I suppose I could have mangled the sensor so it didn't need to be that deep, but I tried without that and got it done with the crowsfoot sensor tool. It slipped a few times but didn't strip the nut. The deep socket would have been easier and if I had to do it again I'd either get a really deep socket or look into hot tips for mangling that sensor.
2) I tried using an impact ratchet, but it didn't have enough oomph. No chance of getting the impact wrench in there.

P.S. hot tip from my Amazon surfing (may be here, too, somewhere in the middle, IDK) -- get the o2 sensor tool, sure. But that is mainly for installing. For removal, particularly if the sensor is giving you a tough time, cut wires and use a real 6 pt deep well socket. The split tools have a tendency to round the plug. It looked to me like the deep well socket would give you a slightly better angle with the breaker bar from the side, too, but I'm not sure - I used crowsfoot and short extension.

P.S. I cleared codes and ran for a bit, before all the incompletes cleared and I could go pass my MD emissions test, I picked up a P0430 code - Cat Efficiency Below Threshold Bank 2. I guess in the 6 months or so I've been driving around with the bad sensor before finally getting around to fixing it, the exhaust finally gave up. I'm at the muffler shop now and sure enough there a hole in the y-pipe under the heat shields. It all syncs up -- the new code, the increase in exhaust sound I noticed a few months back, the good info on that code I found in another thread here, the Kavanaugh hearings, etc.

They gave me a choice of some spot welds, some chunks of pipe, or a new y. I'm going with the latter, for $500 and not have to come back soon. At least not for this. I hope and don't think that's bad for DC area and compared to what I've seen for dealer quotes, even for just the parts, I'm happy enough. That just ate the money I saved by doing the sensors myself, but at least I should pass the emissions test that is quickly coming due.